The present invention relates to combustion products detectors and, in particular, to combustion products detectors of the battery-powered photoelectric type. The invention relates specifically to the apparatus for testing a combustion products detector.
In order to minimize the current drain on the batteries of a battery-powered photoelectric smoke detector, the device is rendered operative to look for the presence of smoke by sampling the ambient air relatively infrequently, typically on the order of once every ten to thirty seconds. Thus, a control means is provided for periodically actuating the photoelectric sensing means for emitting a flash of light into a smoke chamber to see if any light-reflecting smoke is present. In order to test the operation of the device, it is typically provided with a manually-operated test button. The test button is connected to a reflective member which is movable into the smoke chamber for optical coupling with the photoelectric sensing means. Thus, when the reflector is inserted during test, it's reflective characteristics simulate the presence of smoke and, if the device is operating properly, the alarm signal will be sounded.
However, because the photoelectric sensing means is actuated only infrequently, the user may have to hold the test button in for as long as thirty seconds to keep the reflector in the smoke chamber until the photoelectric sensing means is actuated. This is a considerable inconvenience, particularly in view of the fact that smoke detectors are commonly located on ceilings or other relatively difficult-to-reach locations. Furthermore, because of the relatively long time that he may have to wait in order to properly perform the test function, the user may mistakenly conclude before the end of this time that the device is malfunctioning.
Photoelectric combustion products detectors commonly have a feature whereby the device must detect smoke on two or more consecutive samplings before the alarm is sounded, in order to minimize the chance of spurious or false alarms. Thus, it is known in such devices to increase the sampling rate in response to the first smoke detection, so that the subsequent smoke detections will occur more rapidly. But this does not solve the time delay problem during test, since it does not eliminate the delay before the first detection of simulated smoke.